Portable impact tool



. Nov. 19, 1929. F. mKELssoN 1 1,736,716

PORTABLE IMPACT TOOL Filed March 13, 1929 l'noenior:

Patented Nov. 19, 1929 UNITED STATES PATENT QFFIQFL FRANS MICKELSSON, OF HELSINGFORS, FINLAND PORTABLE IMPACT TOOL Application filed March 13, 1929, Serial No. 346,754, and in Finland September 26, 1928.

This invention relates to portable impact tools and has for its object the provision of a device of the class indicated in which a free striking element is thrown in rapid succession against an anvil by which a suitable recipro-.

catory tool carried by the hammer is actuated. One of the specfic objects of the invention is the provision of such a tool in which the track or runway by which the striking element is guided is circular for a part of its extent, engendering centrifugal force in the striking element, and tangential in other portions of its extent so as to lie substantially parallel to the path of the ball when flung against the anvil through centrifugal force upon its release from the rotating means, and parallel to the path of recoil of the striking element when the latter returns into position to be again engaged by the rotatable element.

Another specific object of the invention is the provision of comparatively noiseless operation, by constructing the striking element and the rotating means therefor of dissimilar substances.

Other objects of the invention will appear as the following description of a preferred embodiment thereof proceeds.

In the accompanying drawings in which similar reference characters are used in the several views to designate the same or like parts,

Fig. 1 is a vertical section taken in a plane perpendicular to the axis of rotation of the rotatable element.

Fi 2 is a similar view taken in a plane parallel to the axis of the rotatable element.

Referring now in detail to the several figures, there is provided a casing 10 which carries at its extremity a suitable tool holder 7 for a reciprocating tool exemplified by the chisel shown at 6. Adjacent tie upper end of the tool holder, the casing is provided with an anvil 5, the latter being reciprocable in the direction of the axis of the tool and being of any suitable construction. The casing is provided with opposite fiat sides 8 and 9 in which the shaft 1 of the rotatable element 2 is journaled. In the embodiment shown, the sliaft 1 is the extension of the armature shaft of the electric motor 11 which is enclosed in a motor casing 12 afiixed to the side of the tool. It is not necessary, however, for the motor to be a unitary part of the hammer, for power may be transmitted to the shaft 1 in any suitable manner.

The rotatable element 2 comprises a pair of vanes 13 and 14, and the casing 10 is provid ed with a circular track or runway 1 lying adjacent the ends of the vanes 13 and 14 sh as to retain a striking element 8. In the pres ent instance the striking element has the form of a freely movable ball. The vanes 13 and 14- are adapted to be rapidly rotated, engendering centrifugal force in the ball 3 so that the ball continuously makes contact with and is guided by the track 4-. Said track for a suitable portion of its length on opposite sides of the casing, deviates from its circular curvature and becomes rectilinear, the rectilinear portions being indicated at 15 and 16 and being tangent to the circular portion so as to merge smoothly therewith. The rectilinear portions extend to opposite sides of the anvil 5 and preferably adjacent to the top thereof. The shaft 1 of the rotatable element is at a distance above the anvil 5 greater than the radial length of the vanes plus the diameter of the ball. Thus in the rotation of the vanes, a certain point is reached between the ends of the vanesand the rectilinear portion of the track on the advance side thereof, in the direction of rotation, at which the ball escapes. from the rotatable element, freely flying by centrifugal force so as to strike the anvil 5 as indicated by the arrow in Fig. 1. In the course of this free movement the ball is merely guided by the rectilinear portion 15 of the track. The ball'3 being formed of elastic material, preferably steel, will recoil from the anvil 5 substantially at the same angle as its angle of incidence, freely travelling parallel to the rectilinear portion 16 of the track and guided thereby, said ball being caught by one of the vanes and returned to its confined position between'the rotatable element and the circular part of the casing. This action is repeated with rapidity in accordance with the speed of rotation of the rotatable element. On account of the relatively rapid speed at which this hammer is adapted to be driven, it is not necessary that the ball be very massive, for the efliciency of the tool depends upon the repeated applications of a small inertia blow rather than upon the slower applications of a larger impactive mass.

In order to render the hammer comparatively noiseless, it is preferable to make the rotatable element of a diflerent substance from that of the ball. For instance, if the latter is made of steel, the rotatable element may advantageously be constructed of a nonmetallic tough material such as fiber or a composition of hard rubber and fiber.

While I have in the above description disclosed What I believe to be a preferred and practical form of the invention, it is to be understood that the device as illustrated is merely exemplary and that the details of construction shown are not to be considered as limitative in their bearing upon the scope of the invention.

What I desire to claim is:

1. A mechanically driven tool comprising a casing having an inside peripheral track having a portion of circular curvature, a ball in said casing, rotatable means engaging said ball and carrying it around said circular portion, thus engendering centrifugal force in said ball, said track having rectilinear portions tangent to said circular portion for permitting release of said ball at a certain point in the rotation of said rotatable means, whereby said ball is flung centrifugally, parallel to one of said rectilinear portions, an anvil in the path of said ball, the other rectilinear portion being parallel to the path of recoil of said ball from said anvil.

2. A mechanically driven tool comprising a casing, an anvil reciprocably mounted in said casing, the latter having a tool receiving portion adjacent said anvil, a vane rotatably mounted insaid casing, a free rolling striker in said casing arranged to be impelled by said vane, the latter being pivoted at a distance from said anvil greater than the radius of the vane plus thediameter of the striker, said casing having an inside peripheral track having a circular portion coaxial with the vane and Within ball-retaining proximity to the ends of said vane, said track having rectilinear converging portions tangent to said circular portion and extending to opposite points adjacent opposite sides of the top of said anvil, said rectilinear portions permitting free travel of said ball to said anvil and free recoil of the same into position of engagement by said vane.

In testimony whereof I have signed my name to this specification.

FRANS MIOKELSSON. 

